Absorbent article including a formed fibrous article

ABSTRACT

The present invention generally relates to a method and apparatus for a making a formed fibrous article and more specifically to method and apparatus for making a formed fibrous article useful as an absorbent core structure in a disposable sanitary article such as a sanitary napkin, panty liner, diaper or the like. The present invention also relates to a disposable sanitary article including a formed fibrous article according to the present invention as a core structure thereof.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 12/855,070, filed Aug. 12, 2010, priority of whichis hereby claimed.

FIELD OF THE INVENTION

The present invention generally relates to a method and apparatus for amaking a formed fibrous article and more specifically to method andapparatus for making a formed fibrous article useful as an absorbentcore structure in a disposable sanitary article such as a sanitarynapkin, panty liner, diaper or the like. The present invention alsorelates to a disposable sanitary article including a formed fibrousarticle according to the present invention as a core structure thereof.

BACKGROUND OF THE INVENTION

Various methods for making formed fibrous articles from fibrousmaterials such as cellulose or the like are well know to those of skillin the art. One common method of manufacturing such formed fibrousarticles consists of defiberizing a starting material and then creatingair-entrained stream of the defiberized material. The air-entraineddefiberized material may be formed into a formed fibrous article throughthe use of a porous mold structure subjected to a vacuum to draw thedefiberized material into the mold.

It is also known that formed fibrous articles of the type describedabove may be subjected to calendering processes to alter the mechanicaland fluid handling properties of such articles. A calendering processused in the art is commonly referred to as “pin calendering”. Pincalendering employs the use of a plurality of pins adapted to compressand densify the article.

A problem associated with pin calendering processes of the typedescribed above is that such processes typically require that a “carrierlayer” be used during the pin-calendering step. “Carrier layer” as usedherein means any material layer used to support the formed fibrousarticle, such as a conveyer belt or an adjacent material layer such arolled nonwoven layer or the like. The use of such a carrier layerincreases complexity of manufacture. In addition, if the carrier layeris a layer intended to be incorporated into the final product, theinclusion of such layer may increase the cost of the final productand/or undesirably affect the fluid handling characteristics of theproduct.

In view of the above the inventors of the present invention havediscovered, and disclosed herein, a method and apparatus for making apin-calendered formed fibrous article that does not require the use of acarrier layer. Formed fibrous articles according to the presentinvention are particularly useful as an absorbent core structure in adisposable sanitary article such as a sanitary napkin, panty liner,diaper or the like.

SUMMARY OF THE INVENTION

In view of the foregoing, the present invention provides

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments of the present invention will now be describedwith reference to the drawings, in which:

FIG. 1 is a side elevation view of an apparatus according to the presentinvention;

FIG. 2 is a detailed perspective view of the forming drum that formspart of the apparatus according to the present invention;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a detailed perspective view of a portion of the forming drumshown in FIG. 2;

FIG. 5 is a side elevation view of the forming drum and a calenderingstation that form part of the apparatus according to the presentinvention;

FIG. 6 is a detailed perspective view of the calendering station shownin FIG. 5, depicting the vacuum roll and calender roll thereof;

FIG. 7 is a sectional view taken along line 7-7 in FIG. 6;

FIG. 8 is detailed perspective view of that portion of calenderingstation vacuum roll circled in FIG. 6;

FIG. 9 is a side elevation view of a pin calendering station that formspart of the apparatus according to the present invention;

FIG. 10 is a detailed perspective view of the pin calendering stationshown in FIG. 9, depicting the vacuum roll and pin calender rollthereof;

FIG. 11 is a detailed plan view of that portion of the pin calender rollcircled in FIG. 10;

FIG. 12 is a sectional view taken along line 12-12 in FIG. 11;

FIG. 13 is sectional view taken along line 13-13 in FIG. 9;

FIG. 14 is a sectional view taken along line 14-14 in FIG. 10;

FIG. 15 is a side elevation view of a transfer wheel that forms part ofthe apparatus according to the present invention;

FIG. 16 is a detailed perspective view of the transfer wheel shown inFIG. 15;

FIG. 17 is a partially cut away view of an absorbent article including aformed fibrous article according to the present invention as anabsorbent core layer thereof; and

FIG. 18 is a detailed perspective view of that portion of the absorbentarticle circled in FIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-16, there is illustrated a preferred apparatus 10for making a formed fibrous article 12 according to the method of thepresent invention.

As shown in FIG. 1, the apparatus 10 according to the present inventiongenerally includes a forming drum 14, a calendering station 16, a pincalendering station 18, and a transfer wheel 20. Certain details of theapparatus 10, such as electrical lines, have been omitted from thefigures to simplify the same. However, these features and other basicelements of the apparatus will be clear to those of skill in the art.

The formed fibrous article 12, which is depicted during various stagesof the method according to the present invention in FIGS. 3, 5-7, 10 and14-16, preferably is formed from cellulosic fibers, and in on preferredembodiment of the invention, includes a mixture of cellulosic fibers andsuperabsorbent polymer. Cellulosic fibers that can be used in the formedfibrous article 12 are well known in the art and include wood pulp,cotton, flax and peat moss. Wood pulp is preferred. Both softwood andhardwood species are useful. Softwood pulps are preferred.

The fibrous article 12 may also contain any superabsorbent polymer(SAP), which are well known in the art. For the purposes of the presentinvention, the term “superabsorbent polymer” (or “SAP”) refers tomaterials, which are capable of absorbing and retaining at least about10 times their weight in body fluids under a 0.5 psi pressure. Thesuperabsorbent polymer particles of the invention may be inorganic ororganic crosslinked hydrophilic polymers, such as polyvinyl alcohols,polyethylene oxides, crosslinked starches, guar gum, xanthan gum, andthe like. The particles may be in the form of a powder, grains,granules, or fibers. Preferred superabsorbent polymer particles for usein the present invention are crosslinked polyacrylates, such as theproduct offered by Sumitomo Seika Chemicals Co., Ltd. Of Osaka, Japan,under the designation of SA70N and products offered by Stockhausen Inc.

The pulp used to form the fibrous article 12 is preferably a bleachedsoftwood pulp, produced by a Kraft process. As shown in FIG. 1, the pulpis provided by the manufacturer as a pulp board 22 in rolled form, theroll identified by the reference numeral 24. The pulp board 22 isconveyed from the roll 24 to a device 26 for grinding the pulp board 22into fibrous pulp 28. The fibrous pulp 28 is released from the grindingdevice 26 into a chamber 30 for holding the fibrous pulp 28. Theapparatus 10 may further optionally include a device 32 for introducingsuperabsorbent polymer into the chamber 30 to thereby form a fibrouspulp and superabsorbent mixture. Any conventional device suitable forthis purpose, and known to those of skill in the art, may be used forintroducing the superabsorbent into the chamber 30.

As best seen in FIG. 3, the chamber 30 has a partially open bottomportion 34 that communicates with the forming drum 14. As seen in FIG.1, the forming drum 14 includes a hollow cylinder 15 that is structuredand arranged to rotate about a fixed axis 17. Any conventional means torotate the cylinder 15, well known to those of skill in the art, may beused to rotate the cylinder 15. As shown in FIGS. 1-4, the cylinder 15has a plurality of molds 36 mounted thereto. As the cylinder 15 rotates,each of the molds 36 are sequentially arranged in communication with theopen portion 34 of the chamber 30 to thereby receive fibrous pulp 28from the chamber 30. In FIG. 1, the cylinder 15 rotates in acounterclockwise manner during operation of the apparatus 10.

As shown in FIGS. 1 and 3, the forming drum 14 further includes a vacuumchamber 38 arranged within the interior of the cylinder 15. The vacuumchamber 38 is arranged in a fixed location relative to the rotatingcylinder 15 and is operably coupled to a vacuum source (not shown). Asbest seen in FIG. 4, the mold 36 includes a porous screen 40 structurein the shape of the formed fibrous article 12 to be formed in the mold36. As the mold 36 passes over the vacuum chamber 38 of the forming drum14 the vacuum functions to draw the fibrous pulp 28 from the chamber 30into the mold 36 by drawing air through the porous screen 40 of the mold36.

As shown in detail in FIG. 4, the mold 36 includes a nonporous mountingplate portion 42 that surrounds the porous screen 40 portion of the mold36. The mounting plate portion 42 of the mold 36 is mounted to theperiphery 44 of the cylinder 15, thereby enabling each of the molds 36to rotate with the rotating cylinder 15.

After the mold 36 is rotated under the partially open bottom portion 34of the chamber 30, the mold 36 is further rotated by the rotatingcylinder 15, and as described in further detail below, the fibrousarticle 12 is then transferred to the calendering station 16.

After formation in the mold 36, the formed fibrous article 12 preferablyhas a basis weight in the range of between about 200 gsm (g/m²) to about400 gsm, a thickness in the range of about 5 mm to about 20 mm, and adensity in the range of about 0.015 g/cc to about 0.03 g/cc.

As shown in FIGS. 1 and 5-7 the calendering station 16 generallyincludes a vacuum roll 42 and an opposed calender roll 44. As best seenin FIG. 6, the vacuum roll 42 is formed from a rotatable cylinder 46that is rotatable about a fixed axis 48. Any conventional means torotate the cylinder 46, well known to those of skill in the art, may beused to rotate the cylinder 46. The cylinder 46 rotates in a clockwisemanner during operation of the apparatus 10, as show in FIG. 1. As bestseen in FIGS. 6 and 8, the cylinder 46 includes a plurality of holes 50that extend from the outer surface 52 of the cylinder 46 to the innersurface 54 of the cylinder 46. As shown in FIG. 6, the surface 47 of thecalender roll 44 is preferably smooth, however the surface 47 of thecalender roll 44 may be provided with surface features if desired.

As shown in FIGS. 5-7, the vacuum roll 42 further includes a vacuumchamber 56 arranged within the interior of the cylinder 46. The vacuumchamber 56 is arranged in a fixed location relative to the rotatingcylinder 46 and is operably coupled to a vacuum source 57 (FIG. 1). Thevacuum chamber 56 is arranged in flow communication with the pluralityof holes 50 that extend through the cylinder 46 and thereby draw airthrough said holes 50.

As shown in FIG. 5, the vacuum chamber 56 is arranged such that itsleading edge 58 is substantially aligned with a trailing edge 60 of thevacuum chamber 38 located within cylinder 15 of the forming drum 14.This arrangement of the vacuum chamber 56 relative to location of thevacuum chamber 38 effectuates a transfer of the formed fibrous article12 from within the mold 36 on the forming drum 14 to the vacuum roll 42.

Once the formed fibrous article 12 has been transferred to the cylinder46 of the vacuum roll 43 the cylinder 46 rotates the fibrous 12 articleuntil the article 12 passes through the nip 62 formed between the vacuumroll 42 and the calender roll 44. The nip 62 preferably uniformlycompresses the fibrous article 12 along its length. The compression ofthe fibrous article 12 results in a reduction in thickness of thearticle 12 and a corresponding increase in density. In a preferredembodiment of the invention the nip 62 has a distance “d” (i.e. thedistance between the surfaces of the opposed rolls) of about 0.9 mm. Thedistance “d” is identified by the reference symbol “d” in FIG. 7.

After passing through the nip 62, the formed fibrous article 12preferably has a thickness in the range of about 0.5 mm to about 3.5 mm,and a density in the range of about 0.06 g/cc to about 0.5 g/cc.

After the article 12 passes through the nip 62 the article 12 is furtherrotated in a clockwise direction by the cylinder 46 of the vacuum roll43, and as will be described in further detail below, transferred to thepin calendering station 18.

As shown in FIGS. 1 and 9-10 the pin calendering station 18 generallyincludes a vacuum roll 64 and an opposed pin calender roll 65. As bestseen in FIG. 10, the vacuum roll 64 is formed from a rotatable cylinder66 that is rotatable about a fixed axis 68. Any conventional means torotate the cylinder 66, well known to those of skill in the art, may beused to rotate the cylinder 66. The cylinder 66 rotates in acounterclockwise direction during operation of the apparatus 10. Asshown in FIG. 10, the cylinder 66 includes a plurality of holes 70 thatextend from the outer surface 72 of the cylinder 66 to the inner surface74 of the cylinder 66. In a preferred embodiment of the invention eachof the plurality of holes 70 has a diameter of about 1.5 mm and isspaced from an adjacent hole by a distance of about 4 mm (center tocenter).

As shown in FIG. 10 the pin calender roll 65 is structured and arrangedto rotate about a fixed axis 67. As shown in FIGS. 10-14 the pincalender roll 65 includes a plurality of individual pins 78 that extendoutwardly from a surface 80 of the roll 65. The individual pins 78 arearranged in one of a plurality of arrays 82 that are arranged over thesurface 80 of the roll 65, as shown in FIG. 10. Each array 82 includes aplurality of the pins 78 and each array 82 is adapted to emboss anindividual formed fibrous article 12. As shown in FIG. 10, each array 82is arranged in spaced relationship to an adjacent array 82. In onepreferred embodiment of the invention each array 82 is adapted touniformly pin emboss the formed fibrous article 12 over its entiresurface. Alternatively, each array 82 may be structured to pin embossonly a portion of the fibrous article, e.g. a central pin embossed zoneextending along the center of the product in a longitudinal directionthereof. In preferred embodiments of the invention each of the pins 78are spaced from an adjacent pin by a distance of about 4 mm (center tocenter), have height of about 1.5 mm and have an effective contact areaof from about 0.8 mm² to about 1.2 mm².

As shown in FIGS. 13 and 14, each of the pins 78 are arranged such thatthey do not overlap with any of the plurality of holes 70 in thecylinder 66 of the vacuum roll 64. This arrangement of the pins 78relative to the holes 70 insures that no pulp is forced into any of theplurality of holes 70, thereby improving the efficiency of pulp use andthe efficiency of the process as a whole.

As shown in FIGS. 9-10 and 13-14, the vacuum roll 64 further includes avacuum chamber 86 arranged within the interior of the cylinder 66. Thevacuum chamber 86 is arranged in a fixed location relative to therotating cylinder 66 and is operably coupled to the vacuum source 57(FIG. 1). The vacuum chamber 86 is arranged in flow communication withthe plurality of holes 70 that extend through the cylinder 66 andthereby draws air through said holes 70.

As shown in FIG. 9, the vacuum chamber 86 is arranged such that itsleading edge 88 is substantially aligned with a trailing edge 90 of thevacuum chamber 56 located within the cylinder 46 of the vacuum roll 42.This arrangement of the vacuum chamber 86 relative to the location ofthe vacuum chamber 56 effectuates a transfer of the formed fibrousarticle 12 from the vacuum roll 42 to the vacuum roll 64.

Once the formed fibrous article 12 has been transferred to the cylinder66 of the vacuum roll 64, the cylinder 66 rotates the formed fibrousarticle 12 until the article 12 passes through the nip 92 formed by thevacuum roll 64 and the pin calender roll 65. The plurality of pins 78 inan individual array 82 function to compress the fibrous article 12 atareas corresponding in location to the pins 78. The compression offibrous article 12 in this manner results in a reduction in thickness ofthe article 12 and a corresponding increase in density in those areas ofthe article 12 corresponding in location to the pins 78.

In a preferred embodiment of the invention the nip 92 has a distance(i.e. the distance between the surfaces of the opposed rolls) of about0.8 mm. Also in a preferred embodiment of the invention the pin calenderroll 65 is heated to a temperature of between about 176° F. to about212° F. by means of any suitable conventional heating means. It has beenfound that heating the pin calender roll 65 in this manner helps preventthe formed fibrous article 12 from adhering to the surface of the pincalender roll 65.

After passing through the nip 92, the fibrous article 12 preferably hasa thickness in the range of about 0.2 mm to about 1.0 mm, and a densityin the range of about 0.1 g/cc to about 0.9 g/cc, in those areascompressed by the pins 78. After passing through the nip 92, the fibrousarticle 12 preferably has a thickness in the range of about 0.8 mm toabout 3.5 mm, and a density in the range of about 0.06 to about 0.5g/cc, in those areas outside the individual pins 78.

After the article 12 passes through the nip 92 the article 12 is furtherrotated in a counter clockwise direction by the cylinder 66 of thevacuum roll 64 as shown and, as will be described in further detailbelow, transferred to the transfer wheel 20.

As shown in FIG. 15 the transfer wheel 20 comprises a vacuum roll 94that is formed from a rotatable cylinder 96 that is rotatable about afixed axis 98. Any conventional means to rotate the cylinder 96, wellknown to those of skill in the art, may be used to rotate the cylinder96. The cylinder 96 rotates in a counterclockwise manner duringoperation of the apparatus 10, as show in FIG. 1. As shown in FIG. 16,the cylinder 96 includes a plurality of holes 100 that extend from theouter surface 102 of the cylinder 96 to the inner surface 104 of thecylinder 96.

As shown in FIGS. 15 and 16, the vacuum roll 94 further includes avacuum chamber 106 arranged within the interior of the cylinder 96. Thevacuum chamber 106 is arranged in a fixed location relative to therotating cylinder 96 and is operably coupled to the vacuum source 57(FIG. 1). The vacuum chamber 106 is arranged in flow communication withthe plurality of holes 100 that extend through the cylinder 96 andthereby draw air through said holes 100.

The transfer wheel 20 further includes a porous conveyor belt 97 thatextends around the cylinder 96 and travels with the cylinder 96, i.e. ina counterclockwise direction shown in FIG. 16.

As shown in FIG. 15, the vacuum chamber 106 is arranged such that itsleading edge 108 is substantially aligned with a trailing edge 110 ofthe vacuum chamber 86 located within the cylinder 66 of the vacuum roll64. This arrangement of the vacuum chamber 106 relative to the locationof the vacuum chamber 86 effectuates a transfer of the formed fibrousarticle 12 from the vacuum roll 64 to the vacuum roll 94. Specifically,formed fibrous article 12 is transferred to the conveyor belt 97 andheld in place by the vacuum chamber 106 that functions to draw airthrough the porous conveyer belt 97 via the holes 100 in the cylinder96.

Once the fibrous article 12 is rotated past vacuum chamber 106, theporous conveyer belt 97 functions to further convey the formed fibrousarticle 12 in a machine direction. The formed fibrous article 12 may beconveyed in a machine direction for incorporation into a final productstructure such as a sanitary napkin, panty liner, incontinence article,diaper or the like.

It is noted that the formed fibrous article 12 is formed andpin-calendered without the use of any “carrier layer”. In addition, isnoted that the fibrous article is transferred from the forming drum 14to the calendering station 16 then to the pin calendering station 18without the use of any “carrier layer”. “Carrier layer” as used hereinmeans any material layer used to support the fibrous article, such as aconveyer belt or an adjacent material layer such a rolled nonwoven layeror the like.

In connection with the various vacuum chambers disclosed herein anysuitable vacuum source may be employed. In a preferred embodiment of theinvention the vacuum source is an air blower having an air flow of about2,200 cubic meters per hour.

Reference is made to FIG. 17 which depicts a disposable absorbentarticle 200 in accordance with the present invention. Althoughdisposable absorbent articles according to the present invention will bedescribed herein with reference to a sanitary napkin 200, otherdisposable absorbent articles such as panty liners, adult incontinencearticles, and diapers are considered within the scope of the presentinvention. The sanitary napkin 200 includes a cover layer 210, anoptional transfer layer 212, an absorbent core 214 and a barrier layer216. The absorbent core 214 layer is formed from a formed fibrousarticle 12 of the type described above.

Main Body—Cover Layer

The cover layer 210 may be a relatively low density, bulky, high-loftnon-woven web material. The cover layer 210 may be composed of only onetype of fiber, such as polyester or polypropylene or it may include amixture of more than one fiber. The cover may be composed ofbi-component or conjugate fibers having a low melting point componentand a high melting point component. The fibers may be selected from avariety of natural and synthetic materials such as nylon, polyester,rayon (in combination with other fibers), cotton, acrylic fiber and thelike and combinations thereof. Preferably, the cover layer 210 has abasis weight in the range of about 10 gsm to about 75 gsm.

Bi-component fibers may be made up of a polyester layer and apolyethylene sheath. The use of appropriate bi-component materialsresults in a fusible non-woven fabric. Examples of such fusible fabricsare described in U.S. Pat. No. 4,555,430 issued Nov. 26, 1985 toChicopee. Using a fusible fabric increases the ease with which the coverlayer may be mounted to the absorbent layer(s) of the article and/or tothe barrier layer 216.

The cover layer 210 preferably has a relatively high degree ofwettability, although the individual fibers comprising the cover may notbe particularly hydrophilic. The cover material should also contain agreat number of relatively large pores. This is because the cover layer210 is intended to take-up body fluid rapidly and transports it awayfrom the body and the point of deposition. Therefore, the cover layercontributes little to the time taken for the napkin 200 to absorb agiven quantity of liquid (penetration time).

Advantageously, the fibers that make up the cover layer 210 should notlose there physical properties when they are wetted, in other words theyshould not collapse or lose their resiliency when subjected to water orbody fluid. The cover layer 210 may be treated to allow fluid to passthrough it readily. The cover layer 210 also functions to transfer thefluid quickly to the underlying layers of the absorbent article. Thus,the cover layer 210 is advantageously wettable, hydrophilic and porous.When composed of synthetic hydrophobic fibers such as polyester orbi-component fibers, the cover layer 210 may be treated with asurfactant to impart the desired degree of wettability.

In one preferred embodiment of the present invention the cover is madefrom a 25 gsm thermally bonded nonwoven material constructed from 100%hydrophilic polypropylene fibers, such nonwoven material beingcommercially available from Polystar Company, Salvador, Brazil under theproduct name Multidenier Telao 25 cover.

Alternatively, the cover layer 210 can also be made of a polymer filmhaving large pores. Because of such high porosity, the film accomplishesthe function of quickly transferring body fluid to the underlying layersof the absorbent article. A suitable cover material of this type iscommercially found on the Stayfree Dry Max Ultrathin product distributedby McNeil-PPC, Inc.

The cover layer 210 may be embossed to the underlying absorbent layersin order to aid in promoting hydrophilicity by fusing the cover to theadjacent underlying layer. Such fusion may be effected locally, at aplurality of sites or over the entire contact surface of cover layer210. Alternatively, the cover layer 210 may be attached to the otherlayers of the article by other means such as by adhesion.

Main Body—Transfer Layer

Adjacent to the cover layer 210 on its inner side and bonded to thecover layer 210 is the optional transfer layer 212. The transfer layer212 provides means for receiving body fluid from the cover layer 210 andholding it until the underlying absorbent core 214 has an opportunity toabsorb the fluid, and therefore acts as a fluid transfer or acquisitionlayer. The transfer layer 212 is, preferably, more dense than and has alarger proportion of smaller pores than the cover layer 210. Theseattributes allow the transfer layer 212 to contain body fluid and holdit away from the outer side of the cover layer 210, thereby preventingthe fluid from rewetting the cover layer 210 and its surface. However,the transfer layer is, preferably, not so dense as to prevent thepassage of the fluid through the layer 212 into the underlying absorbentcore 214.

The transfer layer 212 may be composed of fibrous materials, such aswood pulp, polyester, rayon, flexible foam, or the like, or combinationsthereof. The transfer layer 212 may also comprise thermoplastic fibersfor the purpose of stabilizing the layer and maintaining its structuralintegrity. The transfer layer 212 may be treated with surfactant on oneor both sides in order to increase its wettability, although generallythe transfer layer 212 is relatively hydrophilic and may not requiretreatment. The transfer layer 212 is preferably bonded or adhered onboth sides to the adjacent layers, i.e. the cover layer 210 and theunderlying absorbent core 214.

Examples of suitable materials for the transfer layer 212 are throughair bonded pulp sold by Buckeye Technologies of Memphis, Tenn., underthe designation VIZORB 3008, which has a basis weight of 110 gsm, VIZORB3042, which has a basis weight of 100 gsm, and VIZORB 3010, which has abasis weight of 90 gsm.

Main Body—Absorbent Core

Reference is made to FIG. 18 which depicts an absorbent core 214according to the present invention. The absorbent core 214 consists of aformed fibrous article 12 of the type described herein above.

In one preferred embodiment of the invention, the absorbent core 214 isa blend or mixture of cellulosic fibers and superabsorbent disposedtherein. Cellulosic fibers that can be used in the absorbent core 214are well known in the art and include wood pulp, cotton, flax and peatmoss. Wood pulp is preferred.

The absorbent core 214 can contain any superabsorbent polymer (SAP),which are well known in the art. For the purposes of the presentinvention, the term “superabsorbent polymer” (or “SAP”) refers tomaterials, which are capable of absorbing and retaining at least about10 times their weight in body fluids under a 0.5 psi pressure. Thesuperabsorbent polymer particles of the invention may be inorganic ororganic crosslinked hydrophilic polymers, such as polyvinyl alcohols,polyethylene oxides, crosslinked starches, guar gum, xanthan gum, andthe like. The particles may be in the form of a powder, grains,granules, or fibers. Preferred superabsorbent polymer particles for usein the present invention are crosslinked polyacrylates, such as theproduct offered by Sumitomo Seika Chemicals Co., Ltd. Of Osaka, Japan,under the designation of SA70N and products offered by Stockhausen Inc.

The absorbent core 214 preferably has a total basis weight in the rangeof about 200 gsm to about 400 gsm. In preferred embodiments of thepresent invention the absorbent core 214 includes about 50%-100% pulp byweight and about 0% to about 50% superabsorbent by weight.

As shown in FIG. 18, the absorbent core 214 in accordance with theinvention generally includes a first region 218 and a plurality ofsecond regions 220. The plurality of second regions 220 represent thoseportions of the core 214 that have been compressed by the pins 78 asdescribed above and the first region 218 represents that portion of thecore 214 located outside the areas compressed by the pins 78.

The first region 218 preferably has a thickness in the range of about0.5 mm to about 3.5 mm, and a density in the range of about 0.06 g/cc toabout 0.5 g/cc, and each of the plurality of second regions 220preferably has a thickness in the range of about 0.15 mm to about 0.7mm, and a density in the range of about 0.1 to about 0.9 g/cc. Theabsorbent core preferably includes between about 8 to about 10 secondregions 220 per square cm. Each one of the second regions 220 preferablyhas an individual size ranging from about 0.8 mm² to about 1.2 mm². Theplurality of second regions 220 preferably extend over a surface area ofbetween about 88 mm² and 93.6 mm² (i.e. the summation of the area overwhich the second regions 220 extend). The first region 218 preferablyextends over a surface area of between about 6.4 mm² and 12 mm².

In one specific example of the invention, the absorbent core 214consists of a 305 gsm fluff pulp and superabsorbent mixture, the mixtureincluding about 89% fluff pulp by weight, commercially available asGolden Isles Fluff Pulp 420#HD 7% Moisture, from GP Cellulose,Brunswick, Ga., USA, and 11% superabsorbent polymer by weight,commercially available as Aqua Keep SA70N from Sumitomo Seika ChemicalsCo., Ltd., Osaka, Japan.

Main Body—Barrier Layer

Underlying the absorbent core 214 is a barrier layer 216 comprisingliquid-impervious film material so as to prevent liquid that isentrapped in the absorbent core 214 from egressing the sanitary napkin200 and staining the wearer's undergarment. The barrier layer 216 ispreferably made of polymeric film, although it may be made of liquidimpervious, air-permeable material such as repellent-treated non-wovenor micropore films or foams.

The barrier layer may be breathable, i.e., permits vapor to transpire.Known materials for this purpose include nonwoven materials andmicroporous films in which microporosity is created by, inter alia,stretching an oriented film. Single or multiple layers of permeablefilms, fabrics, melt-blown materials, and combinations thereof thatprovide a tortuous path, and/or whose surface characteristics provide aliquid surface repellent to the penetration of liquids may also be usedto provide a breathable backsheet. The cover layer 210 and the barrierlayer 216 are joined along their marginal portions so as to form anenclosure or flange seal that maintains the absorbent core 214 captive.The joint may be made by means of adhesives, heat-bonding, ultrasonicbonding, radio frequency sealing, mechanical crimping, and the like andcombinations thereof.

In one specific example of the invention, the barrier layer consists ofa liquid impermeable 24 gsm polyethylene film commercially availablefrom Clopay do Brasil, Sau Paulo, SP, Brazil.

Positioning adhesive may be applied to a garment facing side of thebarrier layer 216 for securing the napkin 200 to the garment during use.The positioning adhesive may be covered with removable release paper sothat the positioning adhesive is covered by the removable release paperprior to use.

Absorbent articles of this invention may or may not include wings, flapsor tabs for securing the absorbent article to an undergarment. Wings,also called, among other things, flaps or tabs, and their use insanitary protection articles is described in U.S. Pat. No. 4,687,478 toVan Tilburg; U.S. Pat. No. 4,589,876 also to Van Tilburg, U.S. Pat. No.4,900,320 to McCoy, and U.S. Pat. No. 4,608,047 to Mattingly.

The sanitary napkin 200 of the present invention may be applied to thecrotch by placing the garment-facing surface against the inside surfaceof the crotch of the garment. Various methods of attaching absorbentarticles may be used. For example, chemical means, e.g., adhesive, andmechanical attachment means, e.g., clips, laces, ties, and interlockingdevices, e.g., snaps, buttons, VELCRO (Velcro USA, Inc., Manchester,N.H.), zipper, and the like are examples of the various optionsavailable to the artisan.

Adhesive may include pressure sensitive adhesive that is applied asstrips, swirls, or waves, and the like. As used herein, the termpressure-sensitive adhesive refers to any releasable adhesive orreleasable tenacious means. Suitable adhesive compositions, include, forexample, water-based pressure-sensitive adhesives such as acrylateadhesives. Alternatively, the adhesive composition may include adhesivesbased on the following: emulsion or solvent-borne adhesives of naturalor synthetic polyisoprene, styrene-butadiene, or polyacrylate, vinylacetate copolymer or combinations thereof; hot melt adhesives based onsuitable block copoylmers—suitable block copolymers for use in theinvention include linear or radial co-polymer structures having theformula (A-B)x wherein block A is a polyvinylarene block, block B is apoly(monoalkenyl) block, x denotes the number of polymeric arms, andwherein x is an integer greater than or equal to one. Suitable block Apolyvinylarenes include, but are not limited to Polystyrene,Polyalpha-methylstyrene, Polyvinyltoluene, and combinations thereof.Suitable Block B poly(monoalkenyl) blocks include, but are not limitedto conjugated diene elastomers such as for example polybutadiene orpolyisoprene or hydrogenated elastomers such as ethylene butylene orethylene propylene or polyisobutylene, or combinations thereof.Commercial examples of these types of block copolymers include Kraton™elastomers from Shell Chemical Company, Vector™ elastomers from Dexco,Solprene™ from Enichem Elastomers and Stereon™ from Firestone Tire &Rubber Co.; hot melt adhesive based on olefin polymers and copolymerswhere in the olefin polymer is a terpolymer of ethylene and aco-monomers, such as vinyl acetate, acrylic acid, methacrylic acid,ethyl acrylate, methyl acrylate, n-butyl acrylate vinyl silane or maleicanhydride. Commercial examples of these types of polymers include Ateva(polymers from AT plastics), Nucrel (polymers from DuPont), Escor (fromExxon Chemical).

Any or all of the cover layer 210, transfer layer 212, absorbent core214, barrier layer 216, and adhesive layers may be colored. Suchcoloring includes, but is not limited to, white, black, red, yellow,blue, orange, green, violet, and mixtures thereof. Color may be impartedaccording to the present invention through dying, pigmentation, andprinting. Colorants used according the present invention include dyesand inorganic and organic pigments. The dyes include, but are notlimited to, anthraquinone dyes (Solvent Red 111, Disperse Violet 1,Solvent Blue 56, and Solvent Green 3), Xanthene dyes (Solvent Green 4,Acid Red 52, Basic Red 1, and Solvent Orange 63), azine dyes (Jetblack), and the like. Inorganic pigments include, but are not limitedto, titanium dioxide (white), carbon black (black), iron oxides (red,yellow, and brown), chromium oxide (green), ferric ammonium ferrocyanide(blue), and the like.

Organic pigments include, but are not limited to diarylide yellow AAOA(Pigment Yellow 12), diarylide yellow AAOT (Pigment Yellow 14),phthalocyanine blue (Pigment Blue 15), lithol red (Pigment Red 49:1),Red Lake C (Pigment Red), and the like.

The sanitary napkin 200 may include other known materials, layers, andadditives, such as, foam, net-like materials, perfumes, medicaments orpharmaceutical agents, moisturizers, odor control agents, and the like.The sanitary napkin 200 can optionally be embossed with decorativedesigns.

The sanitary napkin 200 may be packaged as unwrapped absorbent articleswithin a carton, box or bag. The consumer withdraws the ready-to-usearticle as needed. The sanitary napkin 200 may also be individuallypackaged (each absorbent article encased within an overwrap).

Also contemplated by the present invention are asymmetrical andsymmetrical absorbent articles having parallel longitudinal edges, dogbone- or peanut-shaped, as well as articles having a taperedconstruction for use with thong-style undergarments.

From the foregoing description, one skilled in the art can ascertain theessential characteristics of this invention, and without departing fromthe spirit and scope thereof, can make various changes andmodifications. Embodiments set forth by way of illustration are notintended as limitations on the variations possible in practicing thepresent invention.

EXAMPLES

Specific inventive examples of the present invention, and comparativeexamples, are described below.

Inventive Example #1

An example of an sanitary napkin according to the invention wasconstructed as follows. The body facing cover layer was constructed froma 25 gsm thermal bonded nonwoven material constructed from 100%hydrophilic polypropylene fibers, commercially available from PolystarCompany, Salvador, Brazil under the product name Multidenier Telao 25cover.

A 100 gsm transfer layer was arranged below the cover layer, thetransfer layer consisting of an through air bonded pulp commerciallyavailable from Buckeye Technologies, Memphis, Tenn., under thedesignation VIZORB 3042.

A 305 gsm formed fibrous absorbent core was arranged below the transferlayer and was formed by the process described herein above withreference to FIGS. 1-16. The absorbent core included a first region anda plurality of second regions. The first region had a thickness of 1.0mm and a density of 0.30 g/cc. Each of the plurality of second regionshad a thickness of 0.2 mm and a density of 0.54 g/cc. The absorbent coreincluded 9 second regions per square cm. Each one of the second regionshad an individual size of 1.0 mm². The first region extended over asurface area of 9.2 mm² and the plurality of second regions extendedover a surface area of 90.8 mm² (i.e. the summation of the area overwhich the second regions extend).

The absorbent core had a composition of 89% by weight of pulp and 11% byweight of superabsorbent polymer. The pulp was Golden Isles Fluff Pulp420#HD 7% Moisture, commercially available from GP Cellulose, Brunswick,Ga., USA. The superabsorbent polymer was Aqua Keep SA70N commerciallyavailable from Sumitomo Seika Chemicals Co., Ltd., Osaka, Japan.

A barrier layer was arranged below the core and was formed from a 24 gsmpolyethylene film commercially available from Clopay do Brasil, SaoPaulo, SP, Brazil.

Each of the layers of the sanitary article were adhered to one anotherusing a conventional hot melt adhesive.

Inventive Example #2

A sanitary napkin was constructed that had an identical structure toInventive Example #1 but for the fact that the cover thereof wasreplaced with an apertured film cover layer of the type found on theStayfree Dry Max Ultrathin product distributed by the Personal ProductsCompany Division of McNeil-PPC, Inc., Skillman, N.J.

Comparative Example #1

Comparative Example #1, representative of a prior art sanitary napkin,consisted of the Intimus Gel Sensitive, commercially available fromKimberly-Clark Kenko Industria e Comercio Ltda, Sao Paulo, Brazil.

Comparative Example #2

Comparative Example #2, representative of a prior art ultrathin product,was constructed as follows.

The body facing cover layer was constructed from a 25 gsm thermal bondednonwoven material constructed from 100% hydrophilic polypropylenefibers, commercially available from Polystar Company, Salvador, Brazilunder the product name Multidenier Telao 25 cover.

A 100 gsm transfer layer was arranged below the cover layer, thetransfer layer consisting of an through air bonded pulp commerciallyavailable from Buckeye Technologies, Memphis, Tenn., under thedesignation VIZORB 3042.

An absorbent core was arranged below the transfer layer and was formedfrom a 208 gsm highly compressed pulp/superabsorbent mixture including25% superabsorbent by weight, commercially available from EAMCorporation, Jessup, Ga., under the designation NVT 208 gsm, 25% SAP.

A barrier layer was arranged below the core and was formed from a 24 gsmpolyethylene film commercially available from Clopay do Brasil, SaoPaulo, SP, Brazil.

Each of the layers of the sanitary article were adhered to one anotherusing a conventional hot melt adhesive.

Test Procedures

Absorbent articles according to the present invention provide superiorfluid handling characteristics. A number of test procedures aredescribed below that highlight the fluid handling properties ofabsorbent articles according to the present invention. Prior toconducting any of the described test procedures described below the testproduct samples should be conditioned for two hours at 21+/−1° C. and50+/−2% humidity.

Procedure for Measuring Fluid Penetration Time

Fluid Penetration Time is measured by placing a product sample to betested under a Fluid Penetration Test orifice plate. The orifice plateconsists of a 7.6 cm×25.4 cm plate of 1.3 cm thick polycarbonate with anelliptical orifice in its center. The elliptical orifice measures 3.8 cmalong its major axis and 1.9 cm along its minor axis. The orifice plateis arranged such that the center of the orifice is aligned with theintersection of the longitudinal and transverse axis of the article,i.e. at the center of the article.

Test fluid was made of the following mixture to simulate bodily fluids:

49.5% of 0.9% sodium chloride solution (VWR catalog #VW 3257-7), 49.05%Glycerin (Emery 917), 1% Phenoxyethanol (Clariant CorporationPhenoxetol™) and 0.45% Sodium Chloride (Baker sodium chloride crystal#9624-05).

A graduated 10 cc syringe containing 7 ml of test fluid is held over theorifice plate such that the exit of the syringe is approximately 3inches above the orifice. The syringe is held horizontally, parallel tothe surface of the test plate. The fluid is then expelled from thesyringe at a rate that allows the fluid to flow in a stream vertical tothe test plate into the orifice and a stop watch is started when thefluid first touches the sample to be tested. The stop watch is stoppedwhen a portion of the surface of the sample first becomes visible abovethe remaining fluid within the orifice. The elapsed time on the stopwatch is the Fluid Penetration Time. The average Fluid Penetration Time(FPT) is calculated from taking the average of readings from threeproduct samples.

Procedure for Measuring Rewet Potential

The three product samples used for the Fluid Penetration Time (FPT)procedure described above are used for the Rewet Potential testdescribed below.

The rewet potential is a measure of the ability of a napkin or otherarticle to hold liquid within its structure when the napkin contains arelatively large quantity of liquid and is subjected to externalmechanical pressure. The rewet potential is determined and defined bythe following procedure.

The apparatus for the Rewet Potential test is the same as that set forthabove with regard to the FPT test and further includes a quantity of 3inch×4 (7.62 cm×10.16 cm) inch rectangles of Whatman #1 filter paperfrom (Whatman Inc., Clifton, N.J.) and a weighing machine or balancecapable of weighing to an accuracy of +/−.0.001 g, a quantity of saidWhatman paper, a standard weight of 2.22 kg (4.8 pounds) havingdimensions 5.1 cm (2 inches) by 10.2 cm (4.0 inches) by approximately5.4 cm (2.13 inches) which applies a pressure of 4.14 kPa (0.6 psi) overthe 5.1 by 10.2 cm (2 inches by 4 inches) surface.

For purposes of the test procedure set forth herein, the same threeproduct samples used for the fluid penetration test should be used forthe rewet potential test. After the test fluid is applied within theorifice plate in the FPT test described above, and as soon as the coverlayer of the napkin first appears through the top surface of the fluid,the stop watch is started and an interval of 5 minutes is measured.

After 5 minutes have elapsed, the orifice plate is removed and thenapkin is positioned on a hard level surface with the cover layer facingupwards.

A fifteen (15) layer stack of the pre-weighed filter paper is placed onand centered over the wetted area and the standard 2.22 kg weight isplaced on top of the filter paper. The filter paper and the weight arearranged over the absorbent article such that they are centered over thearea to which the fluid was applied. The filter paper and the weight arearranged such that their longer dimensions are aligned with thelongitudinal direction of the product. Immediately after placing thepaper and weight on the product, the stopwatch is started and after a 3minute interval has elapsed the standard weight and filter paper arequickly removed. The wet weight of the filter paper is measured andrecorded to the nearest 0.001 grams. The rewet value is then calculatedas the difference in grams between the weight of the wet 15 layers offilter paper and the dry 15 layers of filter paper. The average RewetPotential is calculated from taking the average of readings from threeproduct samples.

Procedure for Measuring the Thickness of a Sanitary Article

The thickness measurement of the product should be conducted at theintersection of the longitudinal and transverse axis of the article,i.e. at the center of the article. Disposable sanitary articlesaccording to the present invention preferably have a thickness of lessthan 5.0 mm.

The apparatus required to measure the thickness of the sanitary napkinis a footed dial (thickness) gauge with stand, available from Ames, witha 2″ (5.08 cm) diameter foot at a pressure of 0.07 psig (4.826 hPa) anda readout accurate to 0.001″ (0.0254 mm). A digital type apparatus ispreferred. If the sanitary napkin sample is individually folded andwrapped, the sample is unwrapped and carefully flattened by hand. Therelease paper is removed from the product sample and it is repositionedback gently across the positioning adhesive lines so as not to compressthe sample, ensuring that the release paper lies flat across the sample.Flaps (if any) are not considered when taking the thickness reading.

The foot of the gauge is raised and the product sample is placed on theanvil such that the foot of the gauge is approximately centered on thelocation of interest on the product sample. When lowering the foot, caremust be taken to prevent the foot dropping onto the product sample orundue force being applied. A load of 0.07 psig (4.826 hPa) is applied tothe sample and the read out is allowed to stabilize for approximately 5seconds. The thickness reading is then taken. This procedure is repeatedfor three product samples and the average thickness is then calculated.

The measured Fluid Penetration Time, Rewet Potential and ProductThickness of the Inventive Examples and Comparative Examples describedabove are summarized in the table set forth below.

Thickness (mm) FPT (s) Rewet (g) Inventive 2.9 4.5 0.03 Example #1Inventive 3.2 4.0 0.03 Example #2 Comparative 3.8 5.5 0.6 Example #1Comparative 2.2 7.5 0.6 Example #2

As shown above, disposable absorbent articles according to the presentprovide superior fluid handling characteristics.

We claim:
 1. An absorbent article comprising: a liquid permeable coverlayer; a liquid impermeable barrier layer; an absorbent core arrangedbetween the cover layer and barrier layer; wherein the absorbent corecomprises a pin-calendered fibrous formed by way of a pin-calenderingprocess that does not use a carrier layer during the pin-calenderingstep.
 2. The absorbent article according to claim 1, further comprisinga transfer layer arranged between the cover layer and the absorbentcore.
 3. The absorbent article according to clam 1, wherein the pincalendering process comprises conveying the fibrous article through anip defined between a first roll and a second roll without the use of acarrier layer.
 4. The absorbent article according to claim 3, whereinthe first roll comprises a vacuum roll and the second roll comprises apin calender roll.
 5. The absorbent article according to claim 4,wherein a surface of the vacuum roll includes a plurality of holes andthe pin calender roll includes a plurality of pins extending outwardlyfrom a surface of the roll.
 6. The absorbent article according to claim5, wherein each one of the plurality of pins is arranged such that itdoes not overlap with any of the plurality of holes.
 7. The absorbentarticle according to claim 1, wherein the absorbent core includes afirst region and a plurality of second regions.
 8. The absorbent articleaccording to claim 7, wherein the first region has a thickness in therange of from about 0.5 mm to about 3.5 mm and a density in the range ofabout 0.06 g/cc and 0.5 g/cc and each of the plurality of second regionshas a thickness in the range of about 0.15 mm to about 0.7 mm and adensity in the range of about 0.1 g/cc and 0.9 g/cc.
 9. The absorbentarticle according to claim 8, wherein the absorbent core includesbetween about 8 and 10 of the second regions per square centimeter. 10.The absorbent article according to claim 9, wherein each of the secondregions preferably has an individual size ranging from about 0.8 mm² toabout 1.2 mm².